April 1996
ATLANTA—The Advisory Committee on Immunization Practices (ACIP) is pursuing its controversial switch to a policy that provides options for polio immunization.
The committee is attempting to integrate into one schedule all possible options for polio immunization: the preferred sequential regimen, which is two doses of inactivated polio vaccine (IPV) followed by two doses of oral polio vaccine (OPV), and the two alternatives, OPV alone or IPV alone.
Although the ACIP has stated its intent to change its recommendation from four doses of OPV to a sequential regimen, the formal statement and recommended schedule have not yet been finalized. A decision on the recommendation is expected at the committee's June meeting and will be published in early 1997.
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OPV is a key component of the global polio eradication effort. It induces stronger mucosal immunity than IPV, and because it is a live vaccine, vaccination of contacts may occur. It also carries a small risk—about 1 in 2.5 million doses distributed—that the live vaccine will cause vaccine-associated paralytic poliomyelitis (VAPP) in vaccinees or their unvaccinated contacts.
Since 1979, the only reported polio in the United States has been associated with the vaccine—about eight to 10 cases per year. Wild polio has not been reported in the Americas since 1991.
By administering two doses of IPV before the first dose of live vaccine, the ACIP hopes to provide the advantages of both vaccines: reduce the incidence of VAPP while retaining the intestinal immunity and secondary immunization of OPV.
Concerns have been expressed about providing options for polio immunization.
Critics maintain that the additional injections and higher cost associated with IPV might reduce compliance, although combination vaccines are being developed. Perhaps most importantly, some involved with global polio eradication are concerned that countries with endemic polio might switch from OPV to IPV.
The ACIP, while sensitive to these arguments, is moving ahead with its intent to revise its polio vaccine recommendations. Although a sequential schedule will be preferred, the statement will give equal weight to all-OPV and all-IPV regimens.
"There is no question as to whether there will be parent and provider choice," said ACIP member Ed Thompson, MD. "The ACIP will make a recommendation for the sequential schedule, but IPV [alone] and OPV [alone] will be acceptable alternatives. We are not in any way considering eliminating choice; we are exercising our responsibility to make a recommendation as to what we believe is best. Parents and providers will have the option of choosing one or the other approaches." Thompson is State Health Officer, Mississippi State Department of Health.
The ACIP is considering a harmonized schedule for polio immunization in which immunizations, whether IPV or OPV, are given at the same ages, said Joel Ward, MD, Chairman of the working group.
Modifications of this schedule are being considered by the ACIP, said Ward, who is Professor of Pediatrics, University of California, Los Angeles.
The current schedule for OPV calls for doses at 2 months, 4 months, between 6 and 18 months, and between 4 and 6 years. The current IPV schedule is for doses at 2 months, 4 months, between 12 and 18 months, and between 4 and 6 years.
The ACIP supported harmonizing the three schedules so that regardless of the vaccination regimen chosen, the same number of doses would be administered at the same ages.
Such a harmonized schedule would eliminate the need to determine which regimen a child began before continuing vaccination with a different provider and would standardize preschool evaluations.
The committee indicated only that it is interested in devising a harmonized polio schedule; the exact schedule has not yet been determined.
In conjunction with the ACIP's revision of polio policy, the American Academy of Pediatrics is also considering adopting a sequential schedule, said Neal Halsey, MD, chair of the Committee on Infectious Diseases. No policy has been adopted, but a statement is expected by this summer.
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